This invention relates to a hub assembly which includes a filter medium therein primarily for use in conjunction with a needle or like instrument for injecting medicaments and the like into a recipient. This invention further pertains to a method of fabricating a filter membrane and inserting the same into a hub.
When liquid medicaments are injected into a patient, it is desirable to deliver the intended liquid with as little impurities or extraneous matter as possible. Oftentimes, even though precautions are undertaken during the administration of liquids to prevent contamination, some impurities, such as particulate matter, are introduced into the liquid medicament for the patient. This occurs, at times, when the liquid medicament is transferred from its supply source to the syringeinjection device. Recognizing that the likelihood of a contaminated medicament is minimal at this stage of administration, it has been found desirable to provide a final precaution immediately prior to injecting the medicament into the patient-recipient. This precaution is accomplished by including a filter medium in the needly assembly itself so that as the liquid passes from the syringe into the needle, a final filtration of the liquid is performed.
Syringe or needle assemblies which include a filter medium therein for this final filtration precaution are known in a variety of configurations and structures. Particularly, in U.S. Pat. No. 2,864,366, a hypodermic syringe adapter is disclosed which includes a cup-shaped filter element on the tapered end of the adapter. This adapter with the filter is inserted into the tapered bore of a Luer-type hypodermic needle assembly. The mating tapers of the adapter and the needle assembly combine to retain the cup-shaped filter in place. However, it takes the combination of the adapter and the needle assembly to provide this final filtration feature, which is undesirable in a number of aspects. For example, by placing a cup-shaped filter on the tapered end of the adapter, quick insertion into the tapered bore of the needle assembly is required, otherwise nothing retains the filter thereon, with the possibility that it may fall off or require additional handling to maintain it in place, thereby increasing the likelihood of contamination of the filter medium itself. Moreover, having to include the filter element on the adapter device of this patent means that the needle assembly is not a filtered package in itself; in other words, if the filter is left off the adapter when the same is inserted into the needle assembly, this final filtration step will not be achieved. In this regard, it is preferable to provide a needle assembly which includes therein a filter medium as a complete unit.
U.S. Pat. No. 2,857,913 discloses a Luer-type intravenous hypodermic needle assembly in which a disc-like sheet of filter material is retained within a recess formed in the inlet end of the needle hub. A sleeve, press fit in the recess is intended to maintain the filter in operative position. While this needle filter is a complete unit including a filter element, the disc-like nature of the filter is not completely satisfactory in sealing off the recess around its periphery. In this regard, fluid may travel around the peripheral edges of the filter element instead of passing through the same for filtration purposes.
Accordingly, it can be seen that the deficiencies in the various types of needle assemblies with filtration means therein as described above are indicative of the need for improvements in this field.